you can try and separate them with a childs gate so they can see and sniff, but your puppy would not be able to get to it. alot of times they work this out, is the puppy attacking or playing? someone on the board who has both can probably give you better advice, but this is how someone had told me to do it a long time ago. how old is the cat?
I have a 6 month old puppy ,and 2 cats. Well the puppy loves and I mean LOVES to chase the 2 cats I have . When she does this I yell at her telling her no. Eventually they will start to work it out. a couple of times Heidi has taken good swipes at Piper ,nothing too serious. I just watch them very closely.
No dog is perfect. You can try to seperate them, and bring them together gradually. Never put two animals together when there is any aggression involved. Let them meet blindly. Put your puppy in one rooma nd your cat in another. Rub the cat with a towl, and then bring the towl to the puppy. Rub your puppy with a different towl, and bring that towl to the cat. Let them get use to eachothers sent for about a day.
shepherds can be cat attackers; watch them carefully when the cat is around and don't leave them alone together. get some obedience training with your shepherd if you haven't already, and teach the command "leave it." when she even looks at the cat tell her "leave it."